The invention relates generally to safety systems for motor vehicles, and more particularly to a system and method for improving motor vehicle safety in crash situations by assuring the timely and reliable failure of various mounts (e.g., motor mounts, transmission mounts, axle mounts, etc.) in order to help dissipate kinetic energy during the crash and reduce the shock and deceleration forces acting on the passenger compartment and, ultimately, the vehicle""s passengers.
Given today""s extensive use of motor vehicles, a significant risk exists that a vehicle may crash into objects or other vehicles. The most severe crashes are those in which a vehicle strikes an object and the front of the vehicle crushes rearward toward the passenger compartment. If the crash is severe enough, the engine can be pushed back into the passenger compartment. Significant penetration into or deformation of the passenger compartment can lead to injury or death of the occupant(s). The risk of impact injury to the occupants of military vehicles is even more significant because soldiers do not usually use seat restraints so as not to restrict their movement in time of crisis.
During the high dynamic-loading experienced during a vehicular collision, the passengers of the vehicle are exposed to acceleration forces due to the sudden change of speed of the vehicle. Upon impact, the passengers experience deceleration forces that can be substantially minimized if they are spread over a longer period of time.
Regardless of the kinetic energy present, the sum of the forces acting on the individual components in a system of masses is equal to the sum of the individual masses times their acceleration. Acceleration can be expressed as the change in velocity of a mass over a given amount of time. Passengers inside a moving vehicle along with the moving vehicle can all be seen as individual moving masses in a system of masses. To reduce the deceleration peak forces upon each passenger, it is desirable to create a situation where the time provided for the masses to slow is maximized. Towards this end, the deployment of air bags increases the time that a passenger will experience deceleration.
In addition to air bag restraint systems, a variety of mechanical means are also used to slow the rate of passenger compartment deceleration during impact. In general, these mechanical means allow the forward and rearward portions of a car to absorb energy by crumpling. For example, crumpling of various structural members allows significant bits of time to lapse before the passenger compartment comes to a full stop. This results in deceleration forces being reduced during the slowing of the passenger compartment. While the crumple zones are collapsing, they slow the passenger compartment. Thus, when the vehicle""s rigid safety cage finally comes to a complete stop, the jolt is less severe than if the vehicle was completely rigid and came to an abrupt stop from full speed at impact in a minimal amount of time.
Other mechanical means have been developed to help mitigate the intrusion of the motor/transmission/axle into the passenger compartment during impact. These methods involve mechanical deformation followed by mechanical breakage of bolted or welded metallic mount assemblies. After a severe impact, the motor mounts fail and the engine pivots or falls down allowing more room for the front crumple zone to absorb impact kinetic energy prior to the engine impinging upon the passenger compartment. However, proper failure of mechanical mount assemblies is not always assured or take place in a timely fashion.
Current methods use the mechanical impact forces to deform and then break bolted or welded metallic mount assemblies. Due to the number of mechanical parts needed to fabricate these assemblies and the unpredictability of the impact force vector, these structural members do not work as desired in many instances. That is, the motor/transmission/axle can release at unpredictable times during the accident. For example, if the forward motor mounts or mechanical linkages used to pivot the motor are deformed but do not allow the motor to pivot downward reliably, the motor might impinge upon the passenger compartment after only minimal crunching of the crumple zone. This could result in unnecessary forces being imparted to the occupants and could increase the chance that the motor will deform and/or penetrate into the passenger compartment.
Accordingly, it is an object of the present invention to provide a method and system for improving vehicle safety in a crash situation.
Another object of the present invention is to provide a method and system for dissipating kinetic energy generated during a vehicle crash situation in a predictable fashion.
Yet another object of the present invention is to provide a method and system for the xe2x80x9con commandxe2x80x9d decoupling of various vehicle components from a vehicle safety cage/frame in a crash situation.
Still another object of the present invention is to provide a method and system for assuring the timely and reliable failure of various vehicle mounting assemblies in a crash situation in order to mitigate intrusion of vehicle components into the passenger compartment.
Other objects and advantages of the present invention will become more obvious hereinafter in the specification and drawings.
In accordance with the present invention, a system and method are provided for improving vehicle safety in a crash situation for a vehicle having mountable vehicle components. A plurality of pyrotechnic bolts are used to mechanically couple at least a portion of the vehicle components to the vehicle. A force measuring device coupled to the vehicle measures forces experienced by the vehicle during a crash and produces a signal indicative of these forces. The signal indicative of crash forces is compared with a threshold and an activation signal is generated when the threshold is attained. Failure of the pyrotechnic bolts is initiated in accordance with a prescribed plan when the activation signal is generated. Failure control of the pyrotechnic bolts can be xe2x80x9cpiggy-backedxe2x80x9d on a vehicle""s existing air bag restraint control system. A variety of methods/systems can be used to implement the prescribed plan of bolt failure. Additional safety enhancements can include the use of pyrotechnic pushers to apply forces to vehicle components released by the pyrotechnic bolt failures. Further, energy dissipators can be used to absorb shock while rigid deflectors can be strategically mounted to protect the vehicle passenger compartment and, possibly, change the angular movement of the passenger compartment relative to the axis of crash impact.